f0<->f2 mapping from an execution trace

f0-f2-mapping.md

To get an f0<->f2 mapping for all newly created smart contracts:

1. Walk the execution trace.
2. Ignore sub-trees of the execution trace where the exit code (.MsgRct.ExitCode) is non-zero (i.e., the sub-call reverted).
3. If the sub-trace's .Msg.To is f01 (init actor), the exit code is zero (success), and the method number is 2 (Exec) or 3 (Exec4): decode .MsgRct.Return as ExecReturn (specifically, as a cbor-encoded list of two byte-strings where the first byte-string is the f0 address of the newly created actor and the second byte-string is the f2 address of the newly created actor.